Patent Application
20240131578
The present invention generally relates to methods and systems for investment casting with high performance aluminum alloys; and more particularly to methods and systems for investment casting with high performance aluminum alloys modified with nanoparticles.
Investment casting is an industrial process based on lost-wax casting. Investment casting can produce complicated shapes that would be difficult or impossible with other casting methods. It can also produce products with great surface qualities and low tolerances with minimal surface finishing or machining required. Whereas the investment casting process may produce high quality surface finishes, it also causes slow cooling rate of the alloy. High performance aluminum alloys such as 2xxx series, 6xxx series, and 7xxx series aluminum alloys tend to form interdendritic and coarse microstructures under slow cooling rate. Such microstructures can result in cracks and tears in the finished products. Thus, traditionally, high performance aluminum alloys such as 2xxx series and 7xxx series aluminum alloys are not used in investment casting processes. Improvements on high performance aluminum alloys may be desired to be suitable for investment casting processes.
Methods and systems for investment casting with high performance aluminum alloys modified with nanoparticles are illustrated.
Some embodiments include metal alloy for investment casting, comprising: an aluminum alloy selected from the group consisting of: a 2xx series aluminum alloy, a 2xxx series aluminum alloy, a 6xxx series aluminum alloy, and a 7xxx series aluminum alloy; and at least one type of nanoparticle dispersed in the aluminum alloy; wherein the metal alloy is compatible with an investment casting process.
In some embodiments, the metal alloy is selected from the group consisting of A201, AA2024, AA2219, A206, AA2618, AA5083, AA6013, AA6061, AA6063, AA6069, AA6110A, AA7034, AA7050, AA7075, and AA7068.
In some embodiments, the at least one type of nanoparticle is selected from the group consisting of a metal oxide, a non-metal oxide, a metal carbide, a non-metal carbide, a metal silicide, a metal boride, a metal nitride, and any combinations thereof.
In some embodiments, the at least one type of nanoparticle has a core-shell structure.
In some embodiments, the at least one type of nanoparticle comprises less than or equal to 30 vol. % of the metal alloy.
In some embodiments, the at least one type of nanoparticle comprises 0.1 vol. % to 2 vol. % of the metal alloy.
In some embodiments, the metal alloy is configured to investment cast a part with at least one thickness of greater than or equal to 0.2 mm.
Some embodiments include a method for investment casting comprising:
Some embodiments further comprise anodizing the part with at least one color.
In some embodiments, the aluminum alloy is selected from the group consisting of: a 2xx series aluminum alloy, a 2xxx series aluminum alloy, a 6xxx series aluminum alloy, and a 7xxx series aluminum alloy.
In some embodiments, the aluminum alloy is selected from the group consisting of: A201, AA2024, AA2219, A206, AA2618, AA5083, AA6013, AA6061, AA6063, AA6069, AA6110A, AA7034, AA7050, AA7075, and AA7068.
In some embodiments, the at least one type of nanoparticle comprises a material selected from the group consisting of: a metal oxide, a non-metal oxide, a metal carbide, a non-metal carbide, a metal silicide, a metal boride, a metal nitride, and any combinations thereof.
In some embodiments, the at least one type of nanoparticle has a core-shell structure.
In some embodiments, the at least one type of nanoparticle comprises less than or equal to 30 vol. % of the aluminum alloy.
In some embodiments, the at least one type of nanoparticle comprises 0.1 vol. % to 2 vol. % of the aluminum alloy.
In some embodiments, the part has at least one section with a thickness of greater than or equal to 0.2 mm.
Some embodiments include an investment cast metal part comprising: an aluminum alloy; and at least one type of nanoparticle; wherein the at least one type of nanoparticle is distributed in the aluminum alloy; and wherein the aluminum alloy is selected from the group consisting of a 2xx series aluminum alloy, a 2xxx series aluminum alloy, a 6xxx series aluminum alloy, and a 7xxx series aluminum alloy.
In some embodiments, the aluminum alloy is selected from the group consisting of A201, AA2024, AA2219, A206, AA2618, AA5083, AA6013, AA6061, AA6063, AA6069, AA6110A, AA7034, AA7050, AA7075, and AA7068.
In some embodiments, the at least one type of nanoparticle comprises a material selected from the group consisting of: a metal oxide, a non-metal oxide, a metal carbide, a non-metal carbide, a metal silicide, a metal boride, a metal nitride, and any combinations thereof.
In some embodiments, the at least one type of nanoparticle has a core-shell structure.
In some embodiments, the nanoparticle comprises less than or equal to 30 vol. % of the aluminum alloy.
In some embodiments, the nanoparticle comprises 0.1 vol. % to 2 vol. % of the aluminum alloy.
In some embodiments, the metal part is configured to be anodized with at least one color.
In some embodiments, the metal part has at least one section with a thickness of greater than or equal to 0.2 mm.
Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.
The description will be more fully understood with reference to the following figures, which are presented as exemplary embodiments of the invention and should not be construed as a complete recitation of the scope of the invention. It should be noted that the patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
Turning now to the drawings, methods and systems for investment casting using high performance aluminum alloys are described. Many embodiments implement high performance aluminum alloys modified with nanoparticles for investment casting processes. Investment casting processes in accordance with some embodiments produce high performance aluminum alloy parts with properties including (but not limited to) tight tolerances, smooth surface finish, complex geometries, and/or thin-walled sections. Certain embodiments modify high performance aluminum alloys including (but not limited to) 2xx series, 2xxx series, 6xxx series, and/or 7xxx series with nanoparticles for investment casting processes. The addition of nanoparticles to the high strength aluminum alloys can refine the microstructures of the alloy during the solidification step of the investment casting processes. Nanoparticle modified high strength aluminum alloys can be investment cast to form parts of desired surface finish without post processing and/or parts of complex structures. The nanoparticle modified high performance aluminum alloys can be resistant to hot cracking during investment casting.
For the purpose of this invention, the term high performance aluminum alloy should be interpreted as 2xx series alloys, 7xx series alloys, 2xxx series aluminum alloy, 6xxx series aluminum alloy, 7xxx series aluminum alloy and/or any alloys that are difficult to cast traditionally, except where otherwise noted.
Investment casting processes in accordance with various embodiments of the invention are discussed further below.
Investment casting processes, also known as lost wax processes, can be industrial production methods for metal parts. During the investment casting process, a pattern made of wax can be coated with a refractory material to make a mold. The wax can then be melted away prior to pouring molten metal into the mold. Investment casting is known to be a precision casting process that can produce high accuracy parts with intricate details.
There are several advantages to investment casting processes. Parts of great complexity and intricacy can be cast using investment casting processes. Investment casting can provide close dimensional control and good surface finish. Wax can be recovered and reused to reduce material waste. Investment casting processes can be net shape where additional machining may not be needed.
Parts produced by investment casting processes have various applications in consumer goods, power generation, aerospace, automobiles, jewels, and so on. Various types of metal alloys including (but not limited to) steel, aluminum alloys, copper alloys, can be used in investment casting. Aluminum alloys have been widely used in consumer electronics, automotive, aerospace, ship building and other fields due to its good plasticity, corrosion resistance and light weight. Common aluminum alloys for investment casting include (but are not limited to) 3xx series alloys, such as A356, A360, A380, A383.
High strength aluminum alloys are in high demand for high mobility and energy efficient applications. The 3xx series aluminum alloys have relatively low mechanical strength compared to high performance aluminum alloys including (but not limited to) 2xx series, 2xxx series, 6xxx series, and/or 7xxx series. However, these high performance aluminum alloys are difficult to use to investment cast complex components due to the slow cooling rates of the process. Refractory materials are commonly used in investment casting processes to make molds as they are resistant to decomposition by heat. Due to the use of refractory material molds, the cooling rate of the molten material can be very slow, such as from about 0.21° C./s to about 1.24° C./s, and/or from about 0.32° C./s to about 4.22° C./s. (See, e.g., Yu, J., et al., Int J Adv Manuf Technol, 105, 3531-3542 (2019); Nawrocki, J., et al., Key Engineering Materials, 641, 124-131 (2015); the disclosures of which are incorporated herein by references.) The high performance aluminum alloys under slow cooling rate can start to form large dendritic grains. The change in microstructures of the alloys can lower the strength and ductility of aluminum castings, which can make it unsuitable for high performance structures. Due to the dendrite formation, the microstructure and dendrite arm spacing (DAS) of the dendrite grains can be coarse. Coarse DAS may result in relatively poor tensile ductility and fracture resistance. In addition, the microstructure changes due to the slow cooling rate can make the high performance alloys susceptible to hot-cracking and shrinkage such that it can be difficult to form thin structures and/or complex shapes.
Many embodiments implement nanoparticle modified high strength aluminum alloys in investment casting processes. The nanoparticles in the high strength aluminum alloys can refine the microstructures of the alloy and eliminate hot cracks during the slow solidification step of the investment casting processes.
Many embodiments implement nanoparticle modified high performance alloys including (but not limited to) 2xx series, 2xxx series, 5xxx series, 6xxx series, and/or 7xxx series, in investment casting. The high performance aluminum alloys have good strength, ductility, and fatigue life, as well as thermal conductivity. Examples of high performance alloys that can be modified with nanoparticles and used in investment casting processes include (but are not limited to) A201, AA2024, AA2219, A206, AA2618, AA5083, AA6013, AA6061, AA6063, AA6069, AA6110A, AA7034, AA7050, AA7075, and AA7068. As can readily be appreciated, any of a variety of high performance aluminum alloy can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.
In several embodiments, the addition of nanoparticles to the high performance aluminum alloys enables low cost investment casting processes for the traditional difficult-to-cast wrought aluminum alloys. The presence of nanoparticles in the aluminum alloys in accordance with some embodiments can effectively refine grain structure during the slow cooling process of investment casting. In a number of embodiments, the nanoparticles can restrict grain growth, modify intermetallic, and/or eliminate hot cracking at the low cooling rates under investment casting. In many embodiments, aluminum alloy systems that are traditionally hard to investment cast can be made suitable for investment casting after modification with nanoparticles.
In many embodiments, nanoparticles can be uniformly dispersed in the metal alloy matrix. In a number of embodiments, nanoparticles comprise materials including (but not limited to) ceramics, oxides, nitrides, borides, carbides and other carbon-based particles, metals, and metal alloys. The nanoparticles can be core-shell particles. Examples of the types of nanoparticles that may be dispersed in the aluminum alloy matrices include aluminum oxide nanoparticles, aluminum nitride nanoparticles, silicon carbide nanoparticles, silicon nitride nanoparticles, titanium carbide nanoparticles, titanium boride nanoparticles, titanium carbonitride nanoparticles, and tungsten carbide nanoparticles. In several embodiments, carbon nanotubes may be dispersed in the aluminum alloy matrices in order to enhance the castability of the high performance aluminum alloys. In addition, the nanoparticles can be core-shell type nanoparticles that include a core material and a coating. Examples include SiC nanoparticles coated with SiO, and ceramic nanoparticles coated with a metal such as nickel or silver. (See, e.g., U.S. Pat. No. 9,023,128 B2 to Li et al., the disclosure of which is incorporated herein by reference in its entirety.)
In some embodiments, the nanoparticles can include one or more ceramics, although other nanoparticle materials are contemplated, including metals or other conductive materials. Examples of nanoparticle materials include metal oxides (e.g., alkaline earth metal oxides, post-transition metal oxides, and transition metal oxides, such as aluminum oxide (Al2O3), magnesium oxide (MgO), titanium oxide (TO2), yttrium oxide (Y2O3), magnesium aluminate (MgAl2O4), and zirconium oxide (ZrO2)), non-metal oxides (e.g., silicon oxide (SiO2)), metal carbides (e.g., transition metal carbides, such as titanium carbide (TiC), niobium carbide (NbC), chromium carbide (Cr3C2), nickel carbide (NiC), hafnium carbide (HfC), vanadium carbide (VC), tungsten carbide (WC), and zirconium carbide (ZrC)), non-metal carbides (e.g., silicon carbide (SiC)), metal silicides (e.g., transition metal silicides, such as titanium silicide (Ti5Si3)), metal borides (e.g., transition metal borides, such as titanium boride (TiB2), zirconium boride (ZrB2), hafnium boride (HfB2), vanadium boride (VB2), and tungsten boride (W2B5)), metal nitrides (e.g., transition metal nitrides), metals (e.g., transition metals in elemental form such as tungsten (W)), alloys, mixtures, or other combinations of two or more of the foregoing, and alloys, mixtures, or other combinations of one or more of the foregoing with other elements. Particular examples of suitable nanoparticle materials include transition metal-containing ceramics, where the presence of a transition metal can impart a greater Hamaker constant more closely approaching that of a metal matrix for a reduced van der Waals potential well, such as transition metal carbides, transition metal silicides, transition metal borides, transition metal nitrides, and other non-oxide, transition metal-containing ceramics. (See, e.g., PCT Application No. PCT/US20/27775 to Li et al.; U.S. Pat. No. 9,322,084 B2 to Li et al.; U.S. Pat. No. 11,040,395 B2 to Li et al., the disclosures of which are incorporated herein by reference in its entirety.) The nanoparticles containing ceramics, metals, or other conductive materials can be core-shell particles.
In many embodiments, the nanoparticles may have at least one dimension with an average size of less than about 500 nm. In some embodiments, the nanoparticles may have at least one dimension with an average size of between 1 nm and about 500 nm; between about 1 nm and about 400 nm; between about 1 nm and about 300 nm; between about 1 nm and about 200 nm; between about 1 nm and about 100 nm; between about 1 nm and about 70 nm; between about 1 nm and about 50 nm; between about 1 nm and about 30 nm. Several embodiments provide that the size distribution of the nanoparticles can be characterized by a standard deviation, relative to an average diameter, that is up to about 100%, up to about 90%, up to about 80%, up to about 70%, up to about 60%, or up to about 50%, of the average size. In certain embodiments, the nanoparticles can have generally spherical or spheroidal shapes, although other shapes and configurations of nanoparticles (such as elliptical shapes, polygon shapes, irregular shapes) can also be contemplated.
In several embodiments, the high performance aluminum alloys can include nanoparticles at a volume percentage in a range from about 0.1% to about 2%; from about 0.25% to 2%; about 0.5% or greater; about 1% or greater; about 2% or greater; about 3% or greater; about 5% or greater; about 6% or greater; about 7% or greater; about 8% or greater; about 9% or greater; about 10% or greater; about 15% or greater; about 20% or greater; about 25% or greater; or about 30% or greater. In certain embodiments, a volume percentage of nanoparticles (from about 0.1% to about 2%) can be applied to investment cast the difficult-to-cast, or traditionally impossible to investment cast, aluminum alloys. As can readily be appreciated, any of a variety of nanoparticle concentration can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.
Investment cast high performance aluminum alloys modified with nanoparticles in accordance with some embodiments exhibit high mechanical strength that are suitable for structural applications. Examples of such aluminum alloys include (but are not limited to) A201, AA2024, AA2219, A206, AA2618, AA5083, AA6013, AA6061, AA6063, AA6069, AA6110A, AA7034, AA7050, AA7075, and AA7068. Any of the above described nanoparticles can be used for modifying the high performance aluminum alloys. Investment casting of such high strength aluminum alloys can open up application space for investment casting aluminum alloys.
Investment casting process can produce parts of thin wall and complex structures. Many embodiments produce investment cast high strength aluminum parts with a thickness between about 0.2 mm and about 0.5 mm; between about 0.2 mm and about 0.3 mm; between about 0.2 mm and about 0.4 mm. Several embodiments produce investment cast high strength aluminum parts with a thickness greater than or equal to about 0.2 mm; greater than or equal to about 0.3 mm; greater than or equal to about 0.4 mm; greater than or equal to about 0.5 mm; greater than or equal to about 0.6 mm; greater than or equal to about 0.7 mm; greater than or equal to about 0.8 mm; greater than or equal to about 0.9 mm; greater than or equal to about 1.0 mm. The hot cracking resistance of the nanoparticle modified high performance aluminum alloys in accordance with some embodiments enable the production of thin wall structures using investment casting processes.
Certain embodiments provide that post processing can be applied to investment cast aluminum alloys with nanoparticles, although to be clear it is not necessary. The addition of nanoparticles enables investment casting of high performance aluminum alloy parts with high quality (such as smooth and with minimal cracks and/or defects) surface finishes. In several embodiments, post processing such as machining may not be needed for the investment cast aluminum parts with nanoparticles. In many embodiments, anodizing can be applied to the investment cast parts to add desired colors. The investment cast metal parts with nanoparticle modified aluminum alloys can be anodized to add any color of choice including (but not limited to) red, blue, green, yellow, silver, gold, and any combinations thereof. As can readily be appreciated, any of a variety of post processing treatment can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.
Many embodiments implement investment casting processes with high performance aluminum alloys infused with nanoparticles. An investment casting process in accordance with an embodiment of the invention is illustrated in
The desired products can be designed using software such as computer aided design (CAD) software. Various shapes and/or structures can be formed using nanoparticle modified high performance aluminum alloys. Form (203) patterns of the products using wax and/or polymers. The patterns can be 3D printed for rapid manufacturing. Metal molds can also be used for injection molded wax patterns. Form (203) a pattern tree with a plurality numbers of the patterns attached to runner and pouring gate. The pattern tree may not be necessary if a single pattern is to be investment cast. The pattern tree can be coated (204) with a molten refractory material, such as a ceramic material or a ceramic slurry. Examples of the refractory material include (but are not limited to): silica, silica sand, magnesia sand, zircon, various aluminum silicates, and alumina. Binding agents can be mixed with the refractory material to achieve a smooth and thin layer of coating. Once the refractory material coating is dry, the refractory coating forms a mold covering the patterns. Heat the coated pattern tree to melt the wax, and remove (205) the wax and/or polymer to leave behind a hollow shell (also known as the mold). Heating can be achieved via a variety of methods such as induction heating, convection heating, or baking.
The prepared metal alloy mixed with nanoparticles can be melted to form (206) molten metal alloys. The molten aluminum alloy can be poured (207) into the ceramic mold. Once the molten alloy cools and solidifies (208), the metal parts can be retrieved (209). Cooling can be achieved using a variety of cooling rate. The parts can be left at room temperature (about 10° C. to about 25° C.) to cool, or additional cooling methods (such as using fans) can be applied to expedite cooling. The investment cast metal parts can be post processed such as anodizing to add desired colors, and/or machining to improve fine details (not shown). Post processing can be optional.
Investment casting processes of high performance aluminum alloy samples in accordance with an embodiment of the invention are illustrated in
As can be inferred from the above discussion, the above-mentioned concepts can be implemented in a variety of arrangements in accordance with embodiments of the invention. Accordingly, although the present invention has been described in certain specific aspects, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that the present invention may be practiced otherwise than specifically described. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive.
As used herein, the singular terms “a,” “an,” and “the”, may include plural referents unless the context clearly dictates otherwise. Reference to an object in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”
As used herein, the terms “approximately,” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. When used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to +0.1%, or less than or equal to ±0.05%.
Additionally, amounts, ratios, and other numerical values may sometimes be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. For example, a ratio in the range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, but also to include individual ratios such as about 2, about 3, and about 4, and sub-ranges such as about 10 to about 50, about 20 to about 100, and so forth.
The current application claims the benefit of U.S. Provisional Patent Application No. 63/380,224 entitled “Methods and Systems for Investment Casting” filed Oct. 19, 2022. The disclosure of U.S. Provisional Patent Application No. 63/380,224 is hereby incorporated by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63380224 | Oct 2022 | US |
